Section 4: Subsidiary Signals

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A subsidiary signal, where provided, is always associated with (i.e. co-located with) a main signal (see Section 2). When cleared, the subsidiary signal authorises the main signal to be passed at 'danger' for a move along the same running line to which the main signal applies, in circumstances when it is not appropriate to clear the main signal.

A subsidiary signal associated with a semaphore signal would usually take the form of a miniature semaphore arm placed below the main stop arm. On most companies' signals, the subsidiary arm remained in the 'on' position while the main stop arm above it was cleared for a running move [4.1]. On the Midland Railway and the North Eastern Railway, however, the interlocking was arranged such that the subsidiary arm had first to be pulled 'off' before the main stop arm could be cleared [4.2]. In either case, when the main stop arm was 'off', the subsidiary arm could be disregarded by drivers.

The above illustrations serve only to show the positions of the signal arms. For full details of their appearance, refer to Section 2 and the remainder of this section.

Different categories of subsidiary signals exist for specific purposes. A 'calling-on' signal authorises the driver to proceed forward cautiously and indicates that the line towards the next stop signal (or buffer stop where there is no main signal in advance) may be occupied. There were numerous different designs of calling-on signal [4.3 - 4.21]. In 1889, just five companies used calling-on signals; these were the L&YR, the LNWR, the LB&SCR, the LC&DR, and the North London Railway.

In 1893, 'calling-on distant' signals (or 'station distant' signals) were introduced on the North London Railway. They were similar in appearance to ordinary calling-on signals but their arms were fishtailed [4.22] and they were placed below a main distant arm. When cleared, the calling-on distant indicated that the home signal ahead was 'off' but the starting signal was 'on' [4.23]. In accordance with North London Railway practice, rings were fitted to the arms of signals applying to the 'No.1' lines [4.24 & 4.25]. The last calling-on distant was removed in 1940.